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vfourpointone-flashxhigh — 04 / 05

Knot Tension

Two anchors, one rope, one crate, and a ravine full of seawater below. Slack rope hangs the load into the drink; a tight rope holds it high and hauls the tension toward the line's rating. Certify a rig that clears the water and stays under the limit — with margin.

tension—
sag—
clearance—

Pick a rope length and a mass, then certify the rig. The rope is rated to 8.0 kN.

Rigging

The statics are exact, not vibes: the rope runs as two straight segments to the crate, and because the line is treated as massless the tension is the same in both. Solving the segment lengths gives the sag, and vertical equilibrium gives T = mg / (sin θ₁ + sin θ₂). Where the load hangs matters less than you would guess — the two angles trade off, so the tension barely moves — but an off-centre crate rides higher, and height is clearance. Rope length and crate mass are the dials that move the load on the line. Keys: 1 2 3 dials, ← → slide the load, C certify, R reset.